基於Spring depends-on的使用詳解
Spring depends-on的使用
通過在XML中的<bean>裡配置depends-on屬性或者在一個類上使用註解@DependsOn,可以使一個Bean的產生依賴於其他幾個Bean。
請看如下代碼:
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean id="son" class="com.tyyd.lifecallbacks.domain.Son" depends-on="mother"></bean> <bean id="mother" class="com.tyyd.lifecallbacks.domain.Mother"></bean> </beans>
son這個Bean的產生依賴於mother這個Bean。
Spring Depends-On 不起作用
beans-realation.xml
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:util="http://www.springframework.org/schema/util" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd"> <!-- abstract="true" 則不能獲得這個bean 說明它隻是一個模板,隻能被繼承 --> <bean id = "address" class="com.yuxishua.autowire.Address" p:city="Beijing" p:street="ChangAnLu" abstract="true"> </bean> <!-- 繼承bean的配置使用parent 屬性,但是沒有java 繼承的意思 --> <bean id = "address2" parent="address" p:street="HanSenLU"> </bean> <!-- 要求person bean 必須有一個關聯的car ,意思就是說這個bean依賴car這個bean --> <bean id = "person" depends-on="car" class="com.yuxishua.autowire.Person" p:name="Tom" p:address-ref="address2" > </bean> <bean id = "car" class="com.yuxishua.autowire.Car" p:brand="AuDi" p:price="30000"> </bean> </beans>
package com.yuxishua.beansrelation; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import com.yuxishua.autowire.Address; import com.yuxishua.autowire.Car; import com.yuxishua.autowire.Person; public class Main { public static void main(String[] args) { ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-realation.xml"); Person person = (Person) ctx.getBean("person"); Address address2 = (Address) ctx.getBean("address2"); Car car = (Car) ctx.getBean("car"); System.out.println(address2 ); System.out.println(person); System.out.println(car); } }
package com.yuxishua.autowire; public class Person { private String name; private Address address; private Car car; @Override public String toString() { return "Person [name=" + name + ", address=" + address + ", car=" + car + "]"; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Address getAddress() { return address; } public void setAddress(Address address) { this.address = address; } public Car getCar() { return car; } public void setCar(Car car) { this.car = car; } }
package com.yuxishua.autowire; public class Car { private String brand; private double price; public String getBrand() { return brand; } public void setBrand(String brand) { this.brand = brand; } public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } @Override public String toString() { return "Car [brand=" + brand + ", price=" + price + "]"; } }
package com.yuxishua.autowire; public class Address { private String city; private String street; @Override public String toString() { return "Address [city=" + city + ", street=" + street + "]"; } public String getCity() { return city; } public void setCity(String city) { this.city = city; } public String getStreet() { return street; } public void setStreet(String street) { this.street = street; } }
就上面的代碼,結果輸出
Person [name=Tom, address=Address [city=Beijing, street=HanSenLU], car=null]
car 為什麼沒有註入呢,是spring版本的問題嗎?還是什麼原因?
spring為4.0.8
以上為個人經驗,希望能給大傢一個參考,也希望大傢多多支持WalkonNet。
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